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ILLINOIS BIOLOGICAL
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Vol. VIII January, 1923 No. i
THE HEAD-CAPSULE OF COLEOPTERA
WITH TWENTY-SIX PLATES
BY
FENNER SATTERTHWAITE STICKNEY
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VOLUME VIII
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Chef's!, n
yf),
TABLE OF CONTENTS
VOLUME VIII
NUMBERS PAGES
1. The head-capsule of Coleoptera. By V . S. Stickney. With 26 plates 1-104
2. Comparative studies on certain features of Nematodes and their sig-
nificance. By D. C. Hetherington. With 4 plates 105-166
3. Parasitic fungi from British Guiana and Trinidad. By F. L. Stevens.
With 19 plates 167-242
4. The external Morphology and Postembryologj' of Noctuid Larvae. By
L. B. Ripley. With 8 plates 243-344
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ILLINOIS BIOLOGICAL
MONOGRAPHS
Vol. VIII January, 1923 No. i
Editorial Committee
Stephen Alfred Forbes William Trelease
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PUBLISEtED UNDER THE
Auspices or the Graduate School by
THE UNn-ERSITY OF ILLINOIS PRESS
Copyright, 1923 by the Univeksity of Ilunois
Distributed June 20, 1923
THE HEAD-CAPSULE OF COLEOPTERA
WITH TWENTY-SIX PLATES
BY
FENNER SATTERTHWAITE STICKNEY
Contributions from the
Entomological Laboratories of the University of Illinois
No. 71
THESIS
SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE
DEGREE OF DOCTOR OF PHILOSOPHY IN ENTOMOLOGY IN THE
GRADUATE SCHOOL OF THE UNIVERSITY OF ILLINOIS
1921
TABLE OF CONTENTS
Introduction 7
Acknowledgment? 9
Materials 10
Head-capsule 16
Epicranial suture 17
Vertex 20
Occipital suture 21
Occiput 21
Compound eyes . . ~~
Oculata 22
Supratentorina 22
Ocelli 23
Antennaria 2,?
Antacoria 23
.\ntacava . 23
Pretentorina -^
Front 24
Clypeus 25
Postcl>-peus 25
Clypealia 25
Mandibularia . 26
Precl>'peus ....,,. 26
Labrum 26
Occipital foramen 27
Submentum 27
Metatentorina 28
Cervix 29
Cervical sderites . 29
Odontoidea . 30
Postgena 30
Gula '. '2
Epicraniura 34
Paracoila 34
Postcoila 34
Precoila 34
Tentorium 35
Pretentorium. .. 36
Metatcntorium. . . 37
Corpotentorium . . 37
Laminatentorium. . 38
Supratentorium 39
Some Phylogenetic Considerations 40
Summarj' 48
Bibliography 50
THE HEAD-CAPSVLE OF COLEOPTERA— STICK SEY
INTRODUCTION
LeConte and Horn published in 1883 a classification of the Coleoptera
that has stood the wear of time remarkably well. Since then, however,
a number of new classifications have been proposed: Lameere (1900 and
1903), Ganglbauer (1892-1904), Handlirsch (1906-1908), Kolbe (1901,
1908, and 1911), Sharp (1909), and Gahan (1911), all of which differ more
or less seriously in one way or another, and show, for one thing, the need
of further comparative morphological data, which is, of course, indispensa-
ble to the building of any thorough classification. Leng's recent catalogue
(1920) also emphasizes this need.
A review of the literature seems to show but few studies based on the
comparative morphology of a comprehensive series of coleopterous fami-
lies. A number of European workers have published comparative studies
of the wings of Coleoptera, the most recent being by d'Orchymont (1920).
Sharp and Muir (1912) and Muir (1918) have published the results of
their investigations on the male genital tube in Coleoptera. Various
internal structures have been discussed from time to time by a number
of workers. Narrower in scope is the work of d'Orchymont (1916) on the
classification of the Hydrophiloidea, based on a study of both the adult
and the larva. Hyslop (1917), Boving and Champlain (1920), Craighead
(1920), and Gage (1920) have published papers on the comparative mor-
phology of various families, based on a study of the larvae. There are prob-
ably other comparative papers more or less extensive in scope, but I have
not been able to find any such literature based on a study of the head-
capsule, though "Crampton (1917, 1920, and 1921) has included the discus-
sion of the coleopterous head in papers not limited to a single order. The
comparative morphology of the head-capsule of some other orders, how-
ever, has been investigated: Peterson (1915) on the Thysanoptera, Peter-
son (1916) on the Diptera, Yuasa (1920) on the Orthoptera, and Hoke
(1923) on the Plecoptera. These simply draw attention to the need of
such an investigation of the head-capsule of Coleoptera.
With the broader vision in mind of a more satisfactory and natural
classification of the Coleoptera, the following study on the comparative
morphology of the head-capsule is offered. This study does not aim by
any means to exhaust the subject. There have been too few species in-
vestigated in each family to justify the making of any sweeping state-
ments. This study can simply point out characteristic conditions of
structures as found in the different species of the families studied, revealing,
8 ILUXOIS BIOLOGICAL MOyOGKAPUS [8
therefore, inharmonies, and perhaps suggesting improvements on the pres-
ent arrangement of the classification.
In order to reach a correct estimate of the degree of speciaHzation of
the various parts of the head-capsule, an hypothetical type, representing
a supposed primitive condition, has been constructed. The structure of
this hypothetical type is based on the structure of the head-capsule of
generalized insects and of generalized adult and larval Coleoptera. Each
structure has been treated separately, starting from the hypothetical type.
The submentum has been included in this study because of its bearing on
certain developmental processes. All statements made refer to the species
listed under "materials" only. The material studied was soaked in a 10%
solution of potassium hydroxide until clarified, then washed in distilled
water to remove the hydroxide, and preserved in 70% alcohol. All dis-
sections were made under a binocular microscope in 70% alcohol in Syra-
cuse watch-glasses.
THE HEAD-CAPSULE OF COLEOPTERASTICKNEY
ACKNOWLEDGMENTS
This study was pursued under the supervision of Professor Alex. D.
MacGillivray, to whom I am under the deepest obligations for all that his
supervision has meant to me in the way of helpful suggestions and real
inspiration. I must further thank him for permission to use his unpub-
lished morphological nomenclature. I am also greatly indebted to Profes-
sor S. A. Forbes for suggestions and for furnishing a large number of species
from the collections of the Illinois State Natural History Survey and from
the collections of the University of Illinois. I am further greatly indebted
to Professor H. F. Wickham of the Iowa State University, who supplied
me with a considerable number of species belonging to rare families; to
Messrs. E. A. Schwarz and H. S. Barber, and the authorities of the United
States National Museum for representatives of twelve very rare families
from the collections of the Museum; to Mr. W. S. Blatchley of Indianapolis
for many very rare species; to Dr. Edwin C. Van Dyke of the University
of California for a specimen of a species of Othnius; and to Professor
Henry C. Fall for a specimen of Hydroscapha. Of the many courtesies
that Dr. Chas. P. Alexander of the Illinois State Natural History Survey
has shown me I am duly appreciative. Finally, to Mrs. Elizabeth Stick-
ney, who has helped me greatly in the preparation of the drawings, I am
under deep obligations.
ILLIXOIS BIOLOGICAL MONOGRAPHS [10
MATERIALS
An effort has been made to make this study as comprehensive as pos-
sible, including not only a wide series of families, but also a representation
of the different subgroups within the families. Of the eighty-one families,
exclusive of the Strepsiptera, listed by LeConte and Horn, representatives
of all are embraced in this study. Leng in his recent catalogue lists one
hundred and nine families. Of these one hundred and five have been stud-
ied and figured, representing one hundred and forty-sLx species. The fami-
lies in Leng's catalog not included in this study are Telegeusidae with one
species, Cerophytidae with two species, Murmidiidae with five species,
and Monoedidae with one species. The fundamental structure of the
head is, except in a few cases, practically similar for the two sexes. The
sex has, therefore, been disregarded, except in the case of the brenthid,
Eupsalis minuta, the female of which has a long slender snout, as contrasted
with the large broad snout of the male. The latter has been figured.
A number of attempts were made to arrange the figures in a linear
series leading from the generalized to the specialized forms. All attempts
proved unsatisfactory. No matter what structure or condition of a struc-
ture was used, the structure showed itself to be unstable within narrow
limits, and therefore could not be relied upon to illustrate a definite line
of development. However, the meagre results obtained in trying to ar-
range the drawings in a linear series emphasized an important fact: that
the various families of Coleoptera and even the subgroups within the
families, have developed along many lines. For this study, the arrange-
ment finally decided on, including the species, is that adopted by Leng.
This arrangement will be valuable, in so far as the head-capsule is con-
cerned, in showing the need for further morphological work towards the
improvement of our classification of the Coleoptera. Owing to the
number of drawings presented in this study it was deemed more practical
to omit detailed descriptions. The salient features, only, of the various
structures are discussed. The following list is arranged according to
Leng's catalog, and includes only those species figured: —
COLEOPTERA
SUBORDER .\DEPH.\G.\
Caraboide.4.
1. Cicindelidae.
Megacephalini.— Tetracha Carolina (Figs. 2, 150, 297, 444).
Cicindehni.— Cicindela formosa (Figs. 3, 151, 298, 445).
11] THE HEAD-CAPS CLE OF COLEOPTERA—SnCKXEV 11
2. Carabidae.
Carabinae. — Calosoma calidum (Figs. 4, 152, 299, 446).
Harpalinae. — Harpalus erraticus (Figs. 5, 23, 24, 153, 300, 447).
3. Amphizoidae. — Amphizoa lecontei (Figs. 6, 154, 301, 448).
4. Omophronidae. — Omophron americanum (Figs. 7, 155, 302, 449).
5. Haliplidae.— Peltodytes 12-punctatus (Figs. 8, 156, 303, 450).
6. Dytiscidae. — Cybister fimbriolatus (Figs. 9, 157, 304, 451).
Gyrinoidea.
7. Gyrinidae. — Dineutes americanus (Figs. 10, 158, 305, 452).
SUBORDER POLYPH.\GA
Hydrophiloidea.
8. Hydrophilidae.
Hydraeninae. — Hydraena marginicollis (Figs. 11, 159, 306, 453).
Hydroscaphinae. — Hydroscapha natans (Figs. 12, 160, 307, 454).
Hydrophilinae. — Hydrous triangularis (Figs. 13, 161, 308, 455).
Hydropliilus obtusatus (Figs. 14, 162, 309, 456).
SiLPIIOIDEA.
9. Platypsyllidae. — Platypsyllus casloris (Figs. 15, 163, 310, 457).
10. Brathinidae.— Brathinus nitidus (Figs. 16, 164, 311, 458).
11. Leptinidae. — Leptinus testaceus (Figs. 17, 165, 312, 459).
12. Silphidae. — Necrophorus carolinus (Figs. 18, 166, 313, 460).
13. Clambidae.— Clambus puberulus (Figs. 19, 167, 314, 461).
14. Scydmaenidae. — Connophron fossiger (Figs. 20, 168, 315, 462).
15. Orthoperidae. — Molamba lunata (Figs. 21, 169, 316).
ST-A-PIIYLINOIDEA.
16. Staphylinidae.
Steninae. — Stenus flavicornis (Figs. 22, 170, 317, 463).
Paederinae. — Gastrolobium bicolor (Figs. 25, 171, 318, 464).
Staphylininae.— Creophilus villosus (Figs. 26, 172, 319, 465).
Tachyporinae. — Tachinus fimbriatus (Figs. 27, 173, 320, 466).
Aleociiarinae.— Aleochara lata (Figs. 28, 174, 321, 467).
17. Pselaphidae.— Pilopius lacustris (Figs. 29, 175, 322, 468).
18. Clavigeridae.— Fustiger fuchsi (Figs. 30, 176, 323).
19. Ptilidae.— Limulodes paradoxus (Figs. 31, 177, 324, 469).
20. Sphaeriidae.— Sphaerius politus (Figs. 32, 178, 325, 470).
21. Scaphidiidae. — Scaphidiumquadriguttatum (Figs. 33, 179,326,471).
22. Sphaeritidae.— Sphaerites glabratus (Figs. 34, 180, 327, 472).
23. Histeridae. — Hister memnonius (Figs. 35, 181, 328, 473).
Cantharoidea.
24. Lycidae.— Calopteron terminale (Figs. 36, 182, 329, 474).
25. Lampyridae. — Photinus pyralis (Figs. 37, 183, 330, 475).
26. Phengodidae. — Phengodes plumosa (Figs. 38, 184, 331, 476).
12 ILUXOIS BIOLOGICAL MOXOGKAPIIS [12
27. Canlharidae.
Chauliognathini. — Chauliognathus pennsylvanicus (Figs. 39, 185,
186, 332,477).
Cantharini.— Cantharis bilineatus (Fig. 187).
28. Melyridae.— Collops nigriceps (Figs. 40, 188, S3S, 478).
29. Cleridae.— Trichodes nutalli (Figs. 41, 189, 334, 479).
30. Corynetidae.— Necrobia rufipes (Figs. 42, 190, 335, 480).
Lymexyloidea.
31. Lyme.xylidae.— Hylecoetus lugubris (Figs. 43, 191, 336, 481).
32. Micromalthidae.— Micromalthus debilis (Figs. 44, 192, 337).
CUPESOIDEA.
33. Cupesidae.— Cupes concolor (Figs. 45, 193, 338, 482).
MORDELLOIDEA.
34. Cephaloidae.— Cephaloon lepturides (Figs. 46, 194, 339, 483).
35. Oedemeridae. — Nacerda melanura (Figs. 47, 195, 340, 484).
36. Mordellidae.— Tomoxia bidentata (Figs. 48, 196, 341, 485).
37. Rhipiphoridae. — Macrosiagon dimidiatum (Figs. 49, 197, 342, 486).
38. Meloidae.— Epicauta marginata (Figs. 50, 198, 343, 487).
39. Eurystethidae.— Eurystethus debilis (Figs. 51, 199, 344, 488).
40. Othniidae.— Othnius sp. (Figs. 52, 200, 345, 489).
41. Pythidae.— Pytho planus (Figs. 53, 201, 346, 490).
42. Pyrochroidae. — Neopyrochroa flabellata (Figs. 54, 202, 347, 491).
43. Pedilidae.— Macratria murina (Figs. 55, 203, 348, 492).
44. Anlhicidae.— Noto.xus anchora (Figs. 56, 204, 349, 493).
45. Euglenidae.— Zonantes fasciatus (Figs. 57, 205, 350, 494).
Elateroidea.
46. Cebrionidae.— Cebrio bicolor (Figs. 58, 206, 351, 495).
47. Plastoceridae. — Euthysanius lautus (Figs. 59, 207, 352, 496).
48. Rhipiceridae.— Sandalus niger (Figs. 60, 208, 353, 497).
49. Elateridae.— Alaus oculatus (Figs. 61, 209, 354, 498).
50. Eucnemidae. — Isorhipis ruficornis (Figs. 62, 210, 355, 499).
51. Throscidae.— Throscus chevrolati (Figs. 63, 211, 356, 500).
52. Buprestidae. — Chalcophora virginiensis (Figs. 64, 212, 357, 501).
Dryopoidea.
53. Psephenidae. — Psephenus lecontei (Figs. 65, 213, 358, 502).
54. Dryopidae.— Helichus striatus (Figs. 66, 214, 359, 503).
55. Elmidae. — Stenelmis siniiata (Figs. 67, 215, 360, 504).
56. Heteroceridae. — Heterocerus undatus (Figs. 68, 216, 361, 505).
57. Georyssidae. — Georyssus californicus (Figs. 69, 217, 362, 506).
Dascilloidea.
58. Dascillidae. — Eurypogon niger (Figs. 70, 218, 363, 507).
59. Eucinetidae. — Eucinetus morio (Figs. 71, 219, 364, 508).
13] THE IlEAD-C.iPSVLE OF COLEOPTERA— STICKS EY 13
60. Cyphonidae.— Cyphon ruficollis (Figs. 11, 220, 365, 509).
61. Chelonariidae. — Chelonarium errans (Figs. 73, 221, 366, 510).
Byrrhoidea.
62. Dermestidae. — Dermestes lardarius (Figs. 74, 222, 367, 511).
63. Byrrhidae. — Byrrhus americanus (Figs. 75, 223, 368, 512).
64. Nosodendridae. — Nosodendron unicolor (Figs. 76, 224, 369, 513).
Rhysodoidea.
65. Rhysodidae. — Rhysodes americanus (Figs. 77, 225, 370, 514).
CuCtJJOIDEA.
66. Ostomidae. — Tenebroides sinuatus (Figs. 78, 226, 371, 515).
67. Xitidulidae.
Nitidulinae. — Phenolia grossa (Figs. 79, 227, 372, 516).
Cryptarchinae. — Glischrochilus fasciatus (Figs. 80, 228, 373, 517).
68. Rhizophagidae. — Rhizophagus bipunctatus (Figs. 81, 229, 374, 518).
69. Monotomidae. — Phyconomus marinus (Figs. 82, 230, 375, 519).
70. Cucujidae.
Cucujini. — Cucujus clavipes (Figs. 83, 231, 376, 520).
Hemipeplini. — Hemipeplus marginipennis (Figs. 84,232,377,521).
71. Erotylidae.
Langurinae. — Languria mozardi (Figs. 85, 233, 378, 522).
Erotylinae. — Megalodacne fasciata (Figs. 86, 234, 379, 523).
72. Derodontidae. — Derodontus maculatus (Figs. 87, 235, 380, 524).
73. Cryptophagidae. — Anchicera ephippiata (Figs. 88, 236, 381, 525).
74. Byturidae. — Byturus unicolor (Figs. 89, 237, 382, 526).
75. Mycetophagidae. — Mycetophagus punctatus (Figs. 90, 238, 383,
527).
76. Colydiidae.
Bothriderini. — Bothrideres geminatus (Figs. 91, 239, 384, 528).
Cerylonini.— Philothermus glabriculus (Figs. 92, 240, 385, 529).
77. Lathrideridae. — Melanophthalma cavicollis (Figs. 93, 241, 386, 530).
78. Mycetaeidae. — Phymaphora pulchella (Figs. 94, 242, 387, 531).
79. Endomychidae. — Endomychus biguttatus (Figs. 95, 243, 388, 532).
80. Phalacridae.— Phalacrus politus (Figs. 96, 244, 389, 533).
81. Coccinellidae. — Hippodamia convergens (Figs. 97, 245, 390, 534).
Adalia bipunctata (Figs. 98, 246, 391, 535).
Tenebrioxoidea.
82. Alliculidae.— Pseudocistela brevis (Figs. 99, 247, 392, 536).
83. Tenebrionidae. — Alobates pennsylvanica (Figs. 100, 248, 393, 537).
Tenebrio molitor (Figs. 101, 249, 394, 538).
Boros unicolor (Figs. 102, 250, 395, 539).
84. Lagriidae. — Arthromacra aenea (Figs. 103, 251, 396, 540).
85. Monommidae.— Hyporphagus sp. (Figs. 104, 252, 397, 541).
86. Melandryidae.— Penthe obliquata (Figs. 105, 253, 398, 542).
14 ILLiyOIS BIOLOGICAL MOXOGRAPIIS [14
87. Ptinidae- Ptinus brunneus (Figs. 106, 254, 399, 543).
88. Anobiidae.— Sitodrepa panicea (Figs. 107, 255, 400, 544).
89. Bostrichidae.— Bostrichus bicornis (Figs. 108, 256, 401, 545).
90. Lyctidae.— Lyctus planicollis (Figs. 109, 257, 402, 546).
91. Sphindidae. — Sphindus americanus (Figs. 110, 258, 403, 547).
92. Cisidae.— Plesiocis cribrum (Figs. Ill, 259, 404, 548).
SCARABAEOIDEA.
93. Scarabaeidae.
Aphodiinae. — Aphodius fimetarius (Figs. 112, 260, 405, 549).
Melolonthinae. — Dichelonyx elongata (Figs. 113, 261, 406, 550).
Rutelinae.— Pelidnota punctata (Figs. 114, 262, 407, 551).
Dynastinae. — Strategus julianus (Figs. 115, 263, 408, 552).
Cetoniinae. — Osmoderma eremicola (Figs. 116, 264, 409, 553).
94. Trogidae.— Trox suberosus (Figs. 117, 265, 410, 554).
95. Lucanidae. — Pseudolucanus capreolus (Figs. 118, 266, 411, 555).
96. Passalidae.— Passalus cornutus (Figs. 119, 267, 412, 413, 556).
Cerambycoidea.
97. Cerambycidae.
Prioninae.
Parandrini. — Parandra brunnea (Figs. 120, 268, 414, 557).
Prionini. — Derobrachus brunneus (Figs. 121, 269, 415, 558).
Cerambycinae.
Spondylini. — Spondylis buprestoides (Figs. 122, 270, 416, 559).
Clytini.— Glycobius speciosus (Figs. 123, 271, 417, 560).
Lamiinae.— Tetraopes tetrophthalmus (Figs. 124, 272, 418, 561).
98. Chrysomelidae.
Donaciinae. — Donacia piscatrix (Figs. 125, 273, 419, 562).
Orsodacninae. — Syneta ferruginea (Figs. 126, 274, 420, 563).
Criocerinae. — Criocerus asparagi (Figs. 127, 275, 421, 564).
Cryptocephalinae. — Cryptocephalus quadruplex (Figs. 128, 276,
422, 565).
Eumolpinae. — Chrysochus auratus (Figs. 129, 277, 423, 566).
Chrysomelinae. — Leptinotarsa decemlineata (Figs. 130, 278, 424,
567).
Galerucinae.— Diabrotica 12-punctata (Figs. 131, 279, 425, 568).
Halticinae.— Blepharida rhois (Figs. 132, 280, 426, 569).
Hispinae. — Anoplitis gracilis (Figs. 133, 281, 427, 570).
Cassidinae. — Chelymorpha argus (Figs. 134, 282, 428, 571).
99. Mylabridae.— Pachymerus gleditsiae (Figs. 135, 283, 429, 572).
Brentoidea.
100. Brentidae.— Eupsalis minuta (Figs. 136, 284, 430, 573).
Curculionoidea.
101. Belidae. — Ithycerus noveboracensis (Figs. 137, 285, 431, 574).
151 THE HEAD-CAPSVLE OF COLEOPTERA—STICKXEY 15
102. Platystomidae.— Eurymyctcr fasciatus (Figs. 138, 286, 432, 575).
103. Curculionidae.
Rhinomacerinae. — Rhinomacer pilosus (Figs. 139, 287, 433, 576).
Rhynchitinae.— Rhynchites bicolor (Figs. 140, 288, 43'4, 577).
Attelabinae.— Attelabus analis (Figs. 141, 289, 435, 578).
Otiorhyncliinae. — Epicaerus imbricatus (Figs. 142, 290, 436,579).
Curculioninae. — Lixus fimbriolatus (Figs. 143, 291, 437, 580).
Thecesterninae. — Thecesternus humeralis (Figs. 144, 292, 438,
581).
Calendrinae. — Sphenophorus aequalis (Figs. 145, 293, 439, 582).
SCOLYTOIDEA.
104. Platypodidae.— Platypus flavicornis (Figs. 146, 294, 440, 583).
105. Scolytidae.
Scolytinae. — Scolytus quadrispinosus (Figs. 147, 295, 441, 584).
Hylesininae. — Dendroctonus valens (Figs. 148, 296, 442, 585).
ILLINOIS BIOLOGICAL MONOGRAPHS [16
HEAD-CAPSULE
There exists a distinct homogeneity in the general character of the
structure of the head-capsule of Coleoptera. Its uniform strong chitiniza-
tion is typical. So is the spacious area occupied by the mouth-parts,
producing a relatively broad cephalic end. Especially characteristic
is the wide space between the occipital foramen and the submentum.
Then, there is that indescribable similarity of structure, even between
groups widely separated, that can best be appreciated from a thorough
knowledge of the morphology. As an illustration, there is little super-
ficial resemblance between Harpalus (Figs. 5 and 153) and Phalacrus
(Figs. 96 and 244), either in external or in internal morphology. Their
distinct differences are merely due to two divergent lines of development.
The structures of the dorsal surface of Phalacrus have become highly
specialized, whereas those of Harpalus are relatively generalized. On
the other hand, on the ventral surface the metatentorina has remained
in a relatively primitive condition in Phalacrus, whereas in Harpalus its
position is highly specialized. The internal structures of Phalacrus are
rudimentary or lacking, while in Harpalus they are in a well developed
primitive state. Considering the degree of generalization of each species,
there can hardly be any question that Harpalus is the more generalized.
The above comparative description simph' illustrates roughly the problems
of complexity of development that are encountered. The two distinctive
kinds of development as shown above for Harpalus and Phalacrus, that of
specialization of the dorsal surface and that of separate specialization of
the ventral surface, do not in the least necessarily parallel one another in
the Coleoptera. Indeed, these two lines of development are predominantly
divergent. In the majority of species, the development is trending towards
the obliteration of sutures and consequent consolidation of sclerites, and
towards the development of a compactness of form of the sclerites that do
not consolidate. The general trend towards a cephalization of migratory
structures is a part of this process, too, as well as the development of a
stronger chitinization of the head-capsule as a whole. The entire phenome-
non appears to be for purposes of strengthening the head. Besides
Phalacrus typical examples are Tenebrioides (Fig. 78), GHschrochilus
(Fig. 80), Megalodacne (Fig. 86), and all the Scarabaeoidea. On the
other hand these processes have lagged behind on the ventral surface in
Phalacrus and others. It is true that the hypothetical type (Fig. 149)
shows a marked cephalization of the submentum, with obliteration of
17] THE HEAD-CAPSVLE OF COLEOPTERA—STICKXEY 17
sutures resulting from this migration. Yet the predominant condition
of the heads studied shows only a certain degree of removal from the
primitive type. Stronger chitinization has probably kept pace with the
cephalization of the dorsal surface, as well as the growing compactness
of such a structure as the submentum. But the very significant structure
of the ventral surface, the metatentorina, only shows a certain degree of
removal from the primitive condition in most of the heads.
Developmental processes such as are discussed above can be best
worked out through a comparative study of a large series of forms. In
fact the determination of the homologies of some structures entering into
these developmental processes, as for example the various changes in
the epicranial suture, and the determination of the nature and line of
development of the area between the occipital foramen and the submentum,
would probably be most difficult without this comparative study. The
chief value of this study lies in all probability in the determination of
homologies, to the end of understanding the lines of development present.
The homology existing between the various structures of the head-capsule
of Coleoptera and other orders of insects, particularly the generalized
orders, seems to work out satisfactorily. From such an homology the
hypothetical type was constructed without much difficulty. In general
appearance the head is oblong and rather flattened dorso-ventrally. Such
a form is fairly characteristic of generalized insects and of the more
generalized Coleoptera. The mouth may be considered as directed
cephalad. Such a direction is representative of the vast majority of
the heads, and for purpose of convenience, at least, the following
discussion considers the head as extending cephalad. Some possible
exceptions in which the head appears to be directed ventrad are
found in Calopteron (Fig. 329), Macrosiagon (Fig. 342), Isorhipis (Fig.
355), Throscus (Fig. 356), Byrrhus (Fig. 368), and a few others. It
should not be forgotten, however, that in primitive insects the mouth is
directed ventrad, and the occipital foramen is on one side instead of at
the opposite end.
The line of closure of the head in the embryo is represented by the
epicranial suture. The complete epicranial suture is typical of generalized
insects. Where it is present in Coleoptera, this denotes a generalized
condition. The primitive form of the epicranial suture is that of a deep
inverted Y, with the cephalic ends of the arms near the lateral border of
the labrum. The hypothetical head is represented as having a complete
epicranial suture. The epicranial stem extends to a transverse line drawn
through the middle of the compound eyes. Branching here the epicranial
arms continue to the margin of the head cephalad of the compound eyes.
A complete epicranial suture is not of general occurrence in the Coleoptera.
It is practically complete in Hydrous (Fig. 13) and Hydrophilus (Fig. 14),
18 ILLINOIS BIOLOGICAL MONOGRAPHS (18
very distinct and sharply invaginated in both, particularly so in the former,
and characteristic in form. Each arm reaches the margin of the head
almost immediately cephalad of a compound eye, and the arms are not as
generalized in position as they are in Epicauta (Fig. 50), where they are
quite distinct. The only other occurrence of a complete epicranial suture
is in Chelymorpha (Fig. 134). Here the arms meet the stem farther caudad
than in the other genera named. The arms in this last genus are distinctly
curved, as contrasted with the more or less straight arms in the above
mentioned genera.
The epicranial arms or some portion of them are present in all Coleop-
tera, except possibly in Calopteron (Fig. 36) and Photinus (Fig. 37).
One or more species of every superfamily of the Adephaga and Polyphaga,
except the Elateroidea,Byrrhoidea, Rhysodoidea,and Rhynchophora, have
the arms complete. In the Caraboidea they are prominent as nearly
straight sutures across the head, as in Tetracha (Fig. 2), Cicindela (Fig. 3),
Calosoma (Fig. 4), and Harpalus (Fig. 5). Their most generalized condi-
tion in the Adephaga is found in Omophron (Fig. 7) in which they extend
from the meson at a sharp angle. Representative species of other super-
families that have the arms complete are: Necrophorus (Fig. 18), Tachinus
(Fig. 27), Chauliognathus (Fig. 39), Cupes (Fig. 45), Cephaloon (Fig. 46),
Notoxus (Fig. 56), Heterocerus (Fig. 68), Eucinetus (Fig. 71), Myceto-
phagus (Fig. 90), Tenebrio (Fig. 101), Bostrichus (Fig. 108), Aphodius
(Fig. 112), and nearly all the Cerambycoidea. Species having parts of the
epicranial stem preserved are not very common. In Omophron (Fig. 7),
Tachinus (Fig. 27), Penthe (Fig. 105), and a number of the Cerambycoidea,
parts of the cephalic end can be identified; in Omophron (Fig. 7), Phengodes
(Fig. 38), Cupes (Fig. 45), Sitodrepa (Fig. 107), Blepharida (Fig. 132),
and a number of the Rhynchophora, parts of the caudal end are present.
Chalcophora (Fig. 64) and Tetraopes (Fig. 124) are peculiar in possessing
practically all of the stem but little of the arms. The arms in Chalcophora
are as short as in any other species studied. Parts of the arms are present
in every degree of length from nearly meeting on the meson, as in Nosoden-
dron (Fig. 76), to almost complete disappearance as in Chalcophora (Fig.
357) and Rhysodes (Fig. 370). They also show varying degrees of dis-
appearance and invagination, from the deep distinct invaginations of
such forms as Dineutes (Fig. 10), Necrophorus (Fig. 18), Tachinus (Fig.
27), Heterocerus (Fig. 68), and Arthromacra (Fig. 103), to the faint or
slender and shallow or not at all invaginated sutures characteristic of the
Scarabaeoidea.
The character of the invagination associated with the epicranial arms
is not as simple as may be thought. In Harpalus (Figs. 5 and 24), the
epicranial arms extend from the meson along the edge of the invagination
to the pretentorinae, from which they extend to the bottom of the invagi-
19) THE HEAD-CAPSULE OF COLEOPTERA—STICKNEY 19
nation, curve laterad, and continue to the margin of the head. The course
of the epicranial arms can be better understood from Omophron (Fig. 7),
a related genus, which has retained the cephalic portion of the epicranial
stem. The line of the invagination appears to be and often is considered
to be simply the clypeal suture. If a specimen of Harpalus is soaked for a
long time in potassium hydroxide the invagination can be opened and the
various structures in this region studied advantageously. The invagina-
tion when opened (Fig. 24) will be seen to assume a deep wide wedge-
shaped form, extending entirely across the dorsal surface of the head. The
pretentorinae are located on the external dorsal surface just caudad of the
cephalic margin of the invagination. Although the epicranial arms are not
in evidence anywhere between the meson and the pretentorinae, it is
assumed that the cephalic marginal ridge must represent them, since the
pretentorinae are not only located caudad of the invagination, but the
arms are quite distinct, extending from the pretentorinae to the bottom
of the invagination, in which they then curve laterad and continue to the
margin of the head. From a cross-section (Fig. 23) it will be seen that the
pretentorium expands cephalad in characteristic form from the preten-
torina along an epicranial arm to the bottom of the invagination. In
Calosoma (Fig. 4) the same condition of this region is found as in Harpalus.
In Omophron (Fig. 7) the epicranial arms are distinct between the preten-
torinae, extending from the meson along the cephalic border of the invagi-
nation. From Figure 24 it will be observed that the cephalic border of the
invagination in Harpalus is along the imaginary line of the fronto-clypeal
suture. This border may represent the cephalic limit of the front. The
invagination, then, in Harpalus and Calosoma includes the entire front.
The line of the invagination instead of being solely a part of the epicranial
suture is in fact compound in nature, representing the approximation
of the caudal borders of the front and postclypeus, and that part of it
between the pretentorinae may be termed the "clypofrons." Laterad of
the pretentorinae to the margin of the head the line of the invagination is
readily seen to be an approximation of a part of the vertex with the caudal
border of the postclypeus and cannot be included in the clypofrons.
Due to the more primitive position of the epicranial arms in Omophron
the invagination in this genus contains only a part of the front, hence the
line of the invagination between the pretentorinae is simple in nature.
In Tachinus (Fig. 27) the epicranial stem extends distinctly into the in-
vagination, the arms continuing in the same to the margin of the head.
.\s should be expected, the pretentorinae are within the invagination.
The line of the invagination in Tachinus is then of a different character
from that of either Harpalus or Omophron. In Tachinus, it has nothing
whatever to do with the epicranial suture nor with any other suture, being
throughout the approximation of parts of the external dorsal surface of
20 ILLIXOIS BIOLOGICAL MONOGIiAPlIS [20
the vertex and the front. It is obvious from the above discussion of three
types of the invagination associated with the epicranial arms that the
dorsal surface of the head-capsule in Coleoptera must be studied most
carefully before a correct interpretation of the parts can be made. This
is most true in the case of any invagination that may be present. The
latter may not be readily observed when the head-wall is strongly and
darkly chitinized, necessitating treatment of such specimens before the
parts can be clearly made out. In Dermestes (Fig. 74), and perhaps others,
all external trace of the line of the invagination may be lost. In such
cases a true understanding of the parts can only be gained from an ex-
amination of the ental surface of the head. But in specialized forms the
ental indication of the invagination may also be effaced.
The epicranial suture can always be located from the determination of
the position of the pretentorina. The latter is always closely associated
with the epicranial suture, being present either in or just oft" of the suture,
in which case the pretentorina resembles a sort of pocket. There is
usually little difficulty experienced in locating the suture. The cephalic
ends of the arms are the most persistent parts of it, being present when
the remainder of the suture cannot be identified. Interesting examples
are found in most Rhynchophora, where the remnants of the epicranial
arms are represented by short furrows located at the cephalic end of the
snout. The epicranial arms are typically structures of the dorsal aspect,
but with the shifting and modification of other parts of the head may be
confined to the lateral aspect, as in Helichus (Fig. 359), Adalia (Fig. 391),
or to the ventral aspect, as in Cybister (Fig. 157), Hydrous (Fig. 161)
and Phalacrus (Fig. 244). From the preceding discussion of the epicranial
suture it is seen that what appears superficially to be this suture may not
be so. It is a difficult problem to understand the kind and amount of
change that may have taken place. In a number of the Rhynchophora,
for instance, what appears to be the epicranial stem (Figs. 146 and 147)
may be only invaginations, for in these same species are lateral invagina-
tions that are quite similar in form to the so-appearing epicranial stem.
The epicranial stem seems to the writer to hold the strongest claims, so
these invaginations are considered as such. So, in other instances, where
a structure appears to be more definitely the epicranial suture than any-
thing else, it is so interpreted.
That part of the head-capsule not embraced by the three primary
sclerites cephalad of the epicranial arms, the occiput, and the postgena,
constitutes the vertex. Its extent is determined by the form and size
of the three above mentioned areas. For instance, in those species with
much reduced epicranial arms, as in Creophilus (Fig. 26), Adalia (Fig. 98),
and Phalacrus (Fig. 96), the extent of the vertex is correspondingly in-
creased. In the Rhynchophora, as represented by such species as Lixus
2\] THE HEAD-CAPSULE OF COLEOPTERA—STICKNEY 21
(Fig. 143) and Sphenophorus (Fig. 145) it is very extensive, including
practically all of the snout of the dorsal and lateral surfaces. The area
on the lateral surfaces of the head, cephalad of the compound eyes, be-
tween the latter and the epicranial suture, is the gena, a part of the vertex.
The limits of the gena are not definite. The prominent ridge in many
genera, dorso-mesad of each gena and antacoria, is the so called frontal
ridge, that extends in the general direction from the epicranial arms to the
mesal margin of the compound eyes. The frontal ridge is prominent in
Harpalus (Fig. 5), Necrophorus (Fig. 18), Trichodes (Fig. 41), Neopyro-
chroa (Fig. 54), Dermestes (Fig. 74), and many others.
In generalized insects the occipital suture is confined to the ventral or
caudal aspect, beginning near the lateral margin of the postcoila and
extending around the caudal or dorsal margin of the occipital foramen.
In the Coleoptera this suture arises laterad of the postcoila, extends
cephalad for a considerable distance, then cutves abruptly laterad, ex-
tending onto the dorsal aspect of the head, where it joins the suture of the
other side of the meson. The genus Cicindela (Figs. 3, 151, and 298)
possesses the most generalized condition of this suture found in the Coleop-
tera. The cephalic end of the suture is modified into a ridge. This
ridge is considered a later development, and is not shown in the hypothetical
tvpe. It unquestionably represents a part of the occipital suture, and can
be identified in practically all the Coleoptera, as in such widely separated
groups as Molamba (Fig. 168), Nacerda (Fig. 195) and Byturus (Fig. 237).
The occipital suture separates the vertex from the occiput and the post-
gena. Only the Caraboidea seem to possess with certainty an unmodified
occipital suture. In Cicindela (Fig. 3) it is complete and nearly so in
Tetracha (Figs. 2, 150, and 297), but very faint in great part. In Calo-
soma (Fig. 152) the unmodified suture begins farther caudad and is more
distinct. In Omophron (Fig. 302), two short, characteristically curved,
lateral ridges no doubt represent remnants of the occipital suture. The
ridge across the lateral aspect in Peltodytes (Fig. 303) may also represent
this suture. In Cybister (Fig. 157) it is probably represented by the
crescent-shaped suture on the ventral aspect. Ridges and furrows ap-
pearing in the same general location in other species, such as Aleochara
(Fig. 321), Throscus (Fig. 356), Cyphon (Fig. 365), and Aphodius (Fig.
405), may possibly be homologized as occipital sutures. In most cases
these ridges seem to be merely to mark the limits to which the head is
telescoped in the prothorax.
In those species possessing an occipital suture the occiput is recognized
as a distinct area. It includes the region between the occipital foramen
and the occipital suture as far as the postgena, appearing as a sort of broad
band across the dorsal aspect, divided by the epicranial stem and in-
distinguishably fused on the lateral aspect with the postgenae. Examples
22 ILLIXOIS BIOLOGICAL MONOGKAl'llS [22
of a well marked occiput arc present in Tetracha (Fig. 2), Cicindela
(Fig. 3), Calosoma (Fig. 4), and Harpalus (Fig. 5). In Omophron (Fig.
302) the occipital suture is so short that the limits of the occiput cannot be
definitely determined. In those species not possessing a recognizable
unmodified portion of the occipital suture, the limits of the occiput can
only be judged accordingly. Even in generalized insects the occiput is
nearly always fused with the postgenae, and is so represented in the
hypothetical type.
There is a great similarity in the form and location of the compound
eyes. The general form is oval. They are located near the middle of the
lateral margin of the head. Such a form and location is given in the hypo-
thetical type. There are a number of interesting variations in form from
the normal type. Dineutes (Fig. 305) and Tetraopes (Fig. 124) have four
complete eyes. This phenomenon is produced by a projection of a part
of the vertex into the eye that in time completely separates the two halves.
The line of closure between the projection and the opposite side is indicated
by a distinct line — the exoculata. The beginning of such a projection
is shown in Cephaloon (Fig. 46), Epicauta (Fig. 50) and many others.
In Pseudocistela (Fig. 99) and Osmoderma (Fig. 116) the projection ex-
tends more than half-way across the eye. In Throscus (Fig. 63) the
projection nearly separates the two halves. The eyes of Peltodytes
(Fig. 8), Photinus (Fig. 37) and Stenus (Fig. 22) are very large. Unusual
forms of the eyes are found in Hypophagus (Fig. 104), where they are very
long and narrow nearly meeting on the dorso-meson; in Cryptocephalus
(Fig. 128), where they are prominent, crescent-shaped, and extend well
caudad on the dorsal surface; and in Aphodius (Fig. 112), where they are
relatively small and square-like. The eyes of Limulodes (Fig. 324) are
transparent and almost invisible; those of Leptinus (Fig. 312) are com-
pletely wanting.
The oculata is present only on the inside periphery of the eye as a
broad ring-like shelf. It is considered of little importance in this study.
Its general size is indicated by the dotted area within the eyes of Cicindela
(Fig. 298), Dineutes (Fig. 305), Passalus (Fig. 412), and a few others.
In forms with divided eyes the two sides of an oculata are pressed together,
forming an exoculata.
The supratentorinae represent the point of attachment on the head-
capsule of the supratentoria. They are not thought to be primary in-
vaginations, and may probably represent no more than depressions. In
the Coleoptera the supratentorinae are not prominent, as the pretentorinae
and metatentorinae often are. They are situated on the dorsal surface of
the vertex. Their presence is not general, occurring commonly only in the
Staphylinoidea. Outside of this superfamily the supratentorinae are
found only in Phyconomus (Fig. 82) and Philothermus (Fig. 92). The
2i] THE HEAD-CAPSi'LE OF COLEOPTERA—STICKXEV 2?
supratentoria are usually attached to the inner membrane of the body-wall,
but unless an actual mark of their presence is indicated on the external
surface the supratentorinae are not considered as present. In generalized
insects the latter are generally present. Their presence in the Coleoptera
should indicate a primitive state.
In all the Coleoptera examined, no indication of any ocelli has been
observed.
In generalized insects there is a ring-like sclerite surrounding the
periphery of each antacoria. In Coleoptera this sclerite is present, but
it is distinguished from the head-capsule by a ridge only. On most heads
it is considerably reduced in size, about all that can be seen of it externally
being its projection, the antacoila, upon which the scape of the antenna
articulates. On the other hand, in Sandalus (Fig. 553i), Derobrachus (Fig.
120), Tetraopes (Fig. 124), Leptinotarsa (Fig. 130), and .\nopHtis (Fig.
133), the antennaria is quite prominent. The most generalized position
of the antennaria is considered to be on the gena cephalad of the eye,
notwithstanding that in generalized insects the antennariae are quite fre-
quently found distinctly between the eyes. Embryology, however,
shows that the antennae are postoral in origin. Furthermore, in coleop-
terous larvae each antennaria is located cephalad of the ocellarae. Such
a position in coleopterous adults should denote the more generalized condi-
tion. The antennaria is very unstable in position. There is hardly a
superfamily in which it does not appear in both the generalized position
and elsewhere. In the Scarabaeoidea and Cerambycoidea, though the
position of the antennaria varies within certain limits, yet it shows a char-
acteristic location. In the former it is either on the lateral or ventral
aspects, while in the latter it occurs only on the dorsal aspect. In no other
large groups does the antennaria appear so constant in position. In
Calopteron (Fig. 36) and Phengodes (Fig. 38) it is exceptionally large; in
Dineutes (Fig. 305) and Alobates (Fig. 392) it is exceptionally small.
The membrane attaching the antenna to the head-capsule is the
antacoria. In removing the antennae the antacoria is torn, and as it plays
no significant part in this study no attempt was made to represent it in
every case. The antacoria varies in size depending upon the size and
shape of the scape. It is indicated in a number of figures by the stippled
area: Omophron (Fig. 7), Necrophorus (Fig. 313), Calopteron (Fig. 36),
Phengodes (Fig. 38), and Chauliognathus (Fig. 332).
The depression in the vertex, usually in the gena, within which the
antennaria and antacoria are situated is the antacava. It is always pres-
ent, so far as is known, and is developed into a deep socket in Dineutes
(Fig. 305), Connophron (Fig. 315), Scolytus (Fig. 441), and Dendroctonus
(Fig. 442).
The points of invagination of the pretentoria on the head-capsule are
the pretentorinae. They are always located along the epicranial suture
24 lUJXOIS BIOLOGICAL MOyOGRAPIlS (24
in the Coleoptera. In generalized insects and the more generalized
Coleoptera, they are situated on the lateral margin of the head. They
are, therefore, represented in this position on the hypothetical type. The
pretentorinae have been identified in every species studied except possibly
Calopteron (Fig. 36) and Photinus. In the latter they are represented by
depressions caudad of the eyes. Their position along the epicranial suture
varies greatly. In widely separated groups they may be primitively lo-
cated, as illustrated in such diverse forms as Omophron (Fig. 7), Necroph-
orus (Fig. 18), Scaphidium (Fig. 33), Chauliognathus (Fig. 39), Cepha-
loon (Fig. 46), Nacerda (Fig. 47), Alaus (Fig. 61), Phyconomus (Fig. 82),
and Glycobius (Fig. 123). The position of the pretentorina evidently
cannot possess any important significance in every instance, yet its posi-
tion may be characteristic sometimes. In the Scarabaeoidea it is never
on the dorsal surface; in the Cerambycoidea it is always on the dorsal
surface. In this respect, the pretentorinae and the antennariae behave
similarly. As a matter of fact, they are usually associated together, but
there are some striking exceptions. The antennariae of Macrosiagon
(Fig. 49) are located well caudad of the cephalic margin of the eyes, while
the pretentorinae are situated at the ventro-lateral margin of the head
(Fig. 342). The opposite condition is found in Phenolia (Fig. 79). The
antennariae in the vast majority of cases are caudad of the pretentorinae.
The pretentorinae are the great landmarks of the head-capsule. On
their location the determination of the presence and position of the epi-
cranial suture is often dependent, and, consequently, the homologies of
large areas of the head-capsule. A case in point is that of the Rhyncho-
phora, in which the pretentorinae are located near the cephalic end of the
snout, on the dorso-lateral margin. The epicranial suture is reduced to
the very short cephalic ends of the epicranial arms, and though we cannot,
therefore, indicate with precision the cephalic limits of the vertex, its ap-
proximate limits can be judged, which would show the vertex to occupy
nearly all the dorsal and lateral aspects of the snout.
The sclerite embraced by the epicranial arms is the front. In the
hypothetical type (Fig. 1) its caudal and lateral limits are the epicranial
arms. Its cephaHc limit is indistinguishable, since the front is fused with
the postclypeus. The approximate line of fusion is indicated by a dotted
line. There is no external indication in any head of a fronto-clypeal suture.
The size of the front depends upon the position and direction of the
epicranial arms. In those species possessing the inverted Y type of arms,
the front assumes considerable proportions, but where the arms have been
forced into a more or less straight line across the head, the invagination
associated with the epicranial arms includes practically the entire front. As
mentioned previously, the epicranial arms extend in this manner across
the head in a wide series of families. The front must hence assume this
25] THE HEAD-CAPSULE Of COLEOPTERA—STICKXEV 25
form. In just as wide a series of families, the epicranial arms are in
process of disappearing. In such cases, the caudal limits of the front can
only be judged approximately. In great reduction of the arms, as repre-
sented by Phalacrus (Fig. 96) and Macrosiagon (Fig. 49), the vertex,
the front and the postclypeus are indistinguishably fused into one area.
In all species the clypeus is divided into two distinct sclerites, the
postclypeus and the preclypeus. This condition is not present so far as I
know in the more generalized insects such as the Orthoptera and Plecop-
tera. In some Neuroptera, however, the preclypeus is a large character-
istic sclerite, quite similar to what has been designated as the preclypeus
in the Coleoptera. It may possibly represent the extraordinary develop-
ment and differentiation of the labracoria, but its size, shape and form
would militate against such an assumption. It seems much easier to
believe that this area is a true sclerite, and in this discussion it will be so
considered.
The broad cephalic part of the area between the epicranial arms in the
hypothetical type (Fig. 1) represents the postclypeus. In generalized
Coleoptera it is of considerable size if the dorsal surface has retained a
generalized form. The shape, form, and size of the postclypeus is cor-
related with the position and extent of the epicranial arms, which has
already been discussed. In highly specialized forms like the Scarabaeoidea
(Figs. 114, 115, and 116), the postclypeus may be even more extensive.
.-Vmong the Staphylinidae, the postclypeus may be very large in Tachinus
(Fig. 27) and Aleochara (Fig. 28), and very small in Creophilus (Fig. 26).
In Chalcophora (Fig. 357) the cephalic end of the vertex is located on the
ventral aspect of the head, and the postclypeus is reduced to hardly more
than a line. Among the Cerambycoidea the postclypeus is generally very
large. In the Rhynchophora it is quite reduced in size.
The caudo-lateral projection or lobe of the postclypeus is the clypealia.
In Orthoptera and Plecoptera the clypealia is not separated from the re-
mainder of the postclypeus. In the larvae of CorydaHs it is a prominent
distinct sclerite. The clypealia in the Coleoptera is often separated from
the postch^peus proper by a distinct furrow or suture. It is quite loosely
attached to the postclypeus in the Cicindelidae (Figs. 297 and 298), the
Carabidae (Figs. 299 and 300), many of the Cerambycoidea (Figs. 419 and
424), and others. Difficulty is often experienced in removing the mandi-
bles from the head without detaching the clypealia. The close resemblance
between the Neuroptera and the Coleoptera in other respects would lead
one to beheve that this similar structure in the two orders must be ho-
mologous. The presence of this furrow in the Coleoptera is wide-spread,
as a glance at the figures will show. It can probably show little signifi-
cance as an indication of primitiveness. It must, though, have been
present in the primitive Coleoptera, and is hence shown in the hypothetical
type.
26 ILIjyOIS BIOLOGICAL MONOGRAPHS [26
In most of the Orthoptera a small triangular area is present, extending
from the precoila to the cephalic end of the occipital suture. This sclerite
is known as the mandibularia. No such area has been located in the
Coleoptera.
The dorsal surface of the larvae of Corydalis is very generalized. On
this surface there is a prominent submembranous sclerite between the
postclypeus and the labrum, the preclypeus. Such a sclerite, very similar
in size, form, texture, and position, is present in Tachinus (Fig. 27),
Arthromacra (Fig. 103), Trichodes (Fig. 41), and Glycobius (Fig. 123).
This sclerite is considered the preclypeus. Figure 23 is a longitudinal
section of the dorsal aspect of the head of Harpalus, and shows the char-
acteristic position of the preclypeus. It is always present in the Coleop-
tera, though often considerably reduced in size. The precl}-peus is al-
waj's membranous except in Photinus (Fig. 37), where it is chitinized
and the labrum is membranous. Besides the forms mentioned above,
the preclypeus is large and prominent in Necrophorus (Fig. 18), Conno-
phron (Fig. 20), Macratria (Fig. 55), Philothermus (Fig. 92), Hippodamia
(Fig. 97), and many others. Very frequently the cephalic end of the
postclypeus is infolded, thus carr\-ing the preclypeus and the labrum with
it. In such cases the prech'peus cannot be seen from the dorsal aspect.
The preclypeus, no matter how deeply it is infolded, is, except in a few
cases, sharply differentiated from the postclypeus and the labrum. In
GHschrochilus (Fig. 373) and Chauliognathus (Fig. 332) the postclypeus
and the labrum were in such close approximation that the preclypeus could
not be observed until the two above mentioned scJerites were separated,
and this was possible only after long soaking in potassium hydroxide.
In most of the Rhynchophora, due to the fusion or absence of the labrum,
the preclypeus could not be identified. The preclypeus, however, was
prominent in Attelabus (Fig. 141), and somewhat reduced in Epicaerus
(Fig. 290).
The broad prominent sclerite attached to the cephalic end of the
clypeus in generalized insects is the labrum. In Coleoptera possessing
other generalized structures, the labrum is typically of the same general
form. The labrum is shown in the hypothetical type. In position the
hypothetical labrum should be, with the preclypeus, in accordance with
their condition in generalized insects, on the same general level with the
remainder of the dorsal surface. The generalized form and position of
the labrum is present iti every superfamily except the Elateroidea,
Dryopoidea, Rhysodoidea, Scarabaeoidea, and the Rhynchophora, in
which the postclypeus has been infolded, thus forcing the labrum onto
the ventral aspect. All the superfamilies containing species with the
labrum generalized, contain about as many with it in various degrees of
specialization, as to form, size, texture and position. The labrum in Con-
27] THE HEAD-CAPS CLE OF COLEOPTERA—STICKyEV 27
nephron (Fig. 20), Photinus (Fig. 37), Othnius (Fig. 52), Clielonarium
(Fig. 73), Eurymycter (Fig. 138), and others, is large and membranous.
The labrum of Aphodius (Fig. 260) is large but very thin and delicate.
The labrum of Scolytus (Fig. 295) and Dendroctonus (Fig. 296) is prob-
ably membranous. In the latter, a significant looking slightly chitinized
structure is located in the membrane within the mouth that may represent
the labrum. In Thecesternus (Fig. 292) there is a membranous area closely
joined to the postclypeus that probably represents the labrum. In
Eupsalis (Fig. 284), Lixus (Fig. 291), Sphenophorus (Fig. 293), and
Rhynchites (Fig. 288), there is an area within the mouth, bounded by
furrows, that may be the labrum. Such are particularly suggestive in
view of the fact that in the same location and lying flat against the post-
clypeus a very thin but a relatively large and well chitinized labrum was
found in Epicaerus (Fig. 290) and Attelabus (Fig. 289). The labrum in
Isorhipis (Fig. 210), Nosodendron (Fig. 224), Phyconomus (Fig. 230),
and Derobrachus (Fig. 269) is considerably reduced in size. It is present
in every species, except possibly the rhynchophorous genera named
above, where it is always said to be wanting.
The prominent opening in the caudal part of the head is known as the
occipital foramen. It is generally very large, but in some species, such as
Connophron (Fig. 168), Cephaloon (Fig. 194), and Macratria (Fig. 203)
is reduced in dimensions, due to the constriction of the caudal end of the
head. In Calopteron (Fig. 182), Photinus (Fig. 183), Alaus (Fig. 209),
and Tetraopes (Fig. 272), the occipital foramen is extraordinarily large.
In order to understand clearly the developmental processes that take
place on the ventral surface, it is necessary to consider a sclerite, belongmg
to the mouth-parts, the submentum. In generalized insects the sub-
mentum is not only adjacent to but is one of the covering parts of the
occipital foramen. Such a position is not found in the Coleoptera. Here,
it is always located cephalad of the occipital foramen, with a distinct area
between the two. In the vast majority of heads this area is very wide.
It is considered as having been present in primitive forms, and is shown on
the hypothetical type. The submentum in generalized insects is a large
quadrangular movable plate. Many genera of Coleoptera show a similar
size, form, and mobility, as in Leptinus (Fig. 165), Necrophorus (Fig. 166),
Stenus (Fig. 170), Nacerda (Fig. 195), Neopyrochroa (Fig. 202), Alaus
(Fig. 209), Heterocerus (Fig. 216), Cyphon (Fig. 220) and Byrrhus (Fig.
223). In these three characters, and the additional one of position in re-
spect to the paracoila, which in generalized insects is normally found
beneath the submentum, that of the Adephaga seems to be the most primi-
tive. The innumerable sizes and forms assumed by this structure through-
out the entire series of families can best be judged by glancing at the figures.
It is extraordinarily large in Rhysodes (Fig. 225).
28 II.U.XOIS BIOLOGICAL MOXOGRAPflS [28
The invaginations on the external surface of the head-capsule of the
metatentoria are the metatentorinae. In the Orthoptera the meta-
tentorinae are located along the cephalo-lateral or ventro-lateral border
of the occipital foramen as invaginations between the maxillariae and the
postgenae. They are not in any way associated with the submentum in
generalized insects or in the Coleoptera. The same relative position of
the metatentorinae is maintained in the Plecoptera. In a number of
Coleoptera, as in Helichus (Fig. 214), Stenelmis (Fig. 215), Heterocerus
(Fig. 216), and even in the platystomid, Eurymycter (Fig. 286), this same
generalized position of the metatentorinae is found. In a number of
Coleoptera the metatentorinae are situated considerably cephalad of
the occipital foramen. The question might be raised as to whether the
metatentorinae that are so located could possibly be more generalized in
position than those situated adjacent to the occipital foramen? In
every instance in which the metatentorinae are located cephalad of the
occipital foramen, a suture connects the metatentorinae with the occipital
foramen. In only a few cases does the suture extend much farther
cephalad than the metatentorinae. This suture in the vast majority of
heads studied does not extend cephalad. It is readily seen how the meta-
tentorinae might be drawn cephalad and as a result a suture be formed
marking their line of migration. In such a process one would naturally
not expect to find a suture located cephalad of the metatentorinae, and
in the cases in which the suture does extend so it is easy to understand
that the force of the cephalic pull might have been communicated to this
region, producing in consequence a suture or invagination. Due to the shape
of the head, it is most difficult to believe that the metatentorinae could be
drawn caudad, and if they were so drawn, it would seem that in this process
there would be formed a suture cephalad of the metatentorinae, marking
the line of migration. In this discussion the generalized position of the
metatentorinae will be considered as that of its generalized position in more
primitive insects, at or near the occipital foramen.
In the development of the coleopterous head the metatentorinae have
shown a tendency to migrate cephalad. The cephalic migration of the
metatentorinae and the ventral migration of the pretentorinae and other
structures, were no doubt due to the same force, the result being a closer
approximation of parts, which naturally supplied increased firmness to the
head's mechanics of operation. The Dryopoidea show the most general-
ized position of the metatentorinae. Genera of this superfamily have been
mentioned above. The Elateroidea probably possess the next most gen-
eralized metatentorinae, such as in Sandalus (Fig. 208) and Alaus (Fig.
209). The Cucujoidea show the metatentorinae just a little removed
from the occipital foramen, as in Megalodacne (Fig. 234), Anchicera (Fig.
236), Philothermus (Fig. 240), and others. In the genera of other super-
29] THE HEAD-CAPSULE OF COLEOPTERA—STICKXEY 29
families, as Nosodendron (Fig. 224), Anoplitis (Fig. 236) and Tetraopes
(Fig. 272), almost the same degree of primitiveness is shown. The large
superfamily Mordelloldea show the metatentorinae to have migrated to
about half the distance between the occipital foramen and the submentum.
This condition is fairly consistent throughout the group. In the Bostri-
choidea, the Scarabaeoidea, and the Cerambycoidea, the metatentorinae
show considerable variation in position. This is shown by a comparison of
their position in Bostrichus (Fig. 256) and Sphindus (Fig. 258). In the
famihes to which Tetracha (Fig. 150), Calosoma (Fig. 152), Cybister
(Fig. 157), Dineutes (Fig. 158), Necrophorus (Fig. 166), and Glycobius
(Fig. 271) belong, the metatentorinae have advanced very far cephalad,
near to the submentum. In Photinus (Fig. 183) and Chauliognathus
(Fig. 185) they are located on or quite near the paracoila.
There is a narrow plate surrounding the lateral and caudal margins
of the occipital foramen in some generalized insects, between which and the
postgenae the metatentorinae are invaginated. This plate has disappeared
in the Coleoptera.
The structure connecting the head-capsule with the prothorax is
called the cervix. It is normally com.posed of membrane, and a number
of cervical sclerites. The size of the cervix depends upon the size of the
occipital foramen, and the degree of mobility of the head. In the Lampy-
roidea and some other forms the cervix is very large. The cervix in
Rhysodes is composed of tough fibrous membrane, quite different in
structure from the normal cervix. In nearlv all of the Rhynchophora the
cervix is heavily supported by strong tendons attached at its cephalic
end. These tendons take care of the added strain on the cervix due to
the elongation of the snout. There are more or less small cervical tendons
appearing occasionally throughout the whole series of famihes studied.
In INIolamba (Fig. 21) the cervix is invaginated within the prothorax,
doubling upon itself. The cervix in Bostrichus (Figs. 256 and 401)
doubles back upon the head-capsule, which is produced into a round
projection.
The most prominent and persistent cervical sclerites are the pleural
cervical sclerites, the cervepisternum and the cervepimeron. The former
is usually the larger of the two, and articulates at its cephalic end either
against an odontoidea or simply against the undifferentiated area sur-
rounded by the occipital foramen. The latter usually extends in a different
direction from the former, and articulates at its cephalic end with the cerve-
pisternum and at its caudal end with the prothorax. In Cantharis (Fig.
187),Macratria (Fig.348),Psephenus (Fig. 358) and others, there is a single
large sclerite present. In the Adephaga, in Leptinus (Fig. 312), Hypor-
phagus (Fig. 397), Pseudocistela (Fig. 392), and many others, there is a
single small subcircular sclerite present. Both of these types probably
Fepicsdt tbe cervepastemnm. In a very iaxge nciaber d gaaat cervical
scisites are ahra\^ wannng. Pmv ar« poariv or not at all dfniuptd ia
t^ CenucbT-ccidea. None of the RhvodbopiKsa sto£ed jMtw^-^*. a
cervkai scierire except Euninvcier Tif . 432 , in vidcii it is Tciy small
The vearrai cerrkai sfkme is tiie cervisteraam. Hister .Tig. 1S1\
Xacerda ils. 195\ Cucujus Tig. 251\ and a ieir others. ptKsess two smaS
cervistensa. wMie Tomaxia Tig. 196 possesses a long narrow one- Tbe
ctavistt^iiiigi is CEi ti^ wboie d infreqnent occurrence. The dorsal
cerrical soeite is calkd xiK cervinotimi. It occurs even kss irequeEtly
ilam ii» cervistern.iLm. Hydious iTig. 13 possesses a snbqisadiangBlar
distiDCtly cMriiiized cerviaorsm. In Aleocbara Tig. 2S ■ the cervinorum
is drvided inro nro distinct lightly cMtinized sabniangiiiar sderites.
T-wo maci larger sqnare-lie sckrites are sdmated caadad of these. All
oi tbe Hydro^^iitjdae and Scarabaeidae possess setaceois cando-lateral
scaeriies. -s-siii do not seem to be present in the other geaera studied.
0«ing to the strong chitiniaitjan of the l^ad and the dose nt of the
head in ihe prothorax. tiffire is little need for a spedal process or projec-
tion on the head for the anicEiation of the cer\-episteninin. Snch a process
is called as odoEtcadea. Sosie of the species in which it does occnr are
ScapfcidrcEi Tig. 179 . Tr-rn^eras Tig. 219 , Cyphon Tig. 220 . Byrrhns
Tig. 223 . Xosooendron Tig. 224 , and Arthromacra Tig. 251 . The
iaiter geaas. ii is Interestiiig to note, possesses no cervefKSiemcin.
Thar pan oif the head-capsnie on the candal suiiace, mesad of the oc-
ripraT sutnre and ventrad of eacii occipct. in generalized orthopterons
iasects is a postgena. The ocdpnt is considered as extending to near the
middie of the dorso-vdtrai length of the occipital iorameru thus limiting
the doiTsal extent of the postgenae. The latter are -sridebr SCTarated from
each other by the oropital foramen. The lateral parts of the large sub-
iwfTinrP! distinctly cmrer the mesal parts of the postgenae. In the Colec^
tea. the ocdjttal snmre separates rhi^ region from the remainder of the
head-cajsnie. as in generalized insects, and the ocdpnt is also indis-
ti^HEhably fnsed with the postgenae. Bnt the postgenae, instead of
bsBg widely 5^)aiated and their mesal parts being covered by the lateral
puts